Radio frequency (RF) sampling transceivers are an emerging trend targeting the next generation of wireless base stations. In an RF sampling transceiver, the conversion between analog and digital signals is performed directly using either a high speed, high performance digital-to-analog converter (DAC) at, e.g., 14 bits, 9 GSPS or an analog-to-digital converter (ADC) at, e.g., 3 GSPS. The high-speed conversion avoids the need for mixers in the RF/analog domain. This architecture can enable simultaneous multi-band transmission, by employing digital up-converters (DUC) for each of the bands, using a single RF/analog transmitter chain. Similarly, the architecture can enable simultaneous multi-band reception, by employing digital down-converters (DDC) for each of the bands, using a single RF/analog receiver chain.
In one example, a complex baseband transmission signal that consists of I (in-phase) and Q (quadrature) signals, at a sampling rate of 500 MHz, is interpolated (e.g., by 18) and up-converted to obtain an RF signal at 9 giga-samples per second (GSPS). However, digital complexity and power consumption of the DUC could be significant, as it needs to interpolate the complex baseband samples to generate the RF DAC samples at GSPS rates, with suppression of the out-of-band images. Cost, which is dependent on the area occupied by the device, and power consumption are key parameters for these applications.